The present invention relates to an organic-inorganic hybrid glassy material where raw materials used in a sol-gel process are starting materials and also to processes for producing the same.
With regard to materials which soften at not higher than 600° C., macromolecular materials, low-melting glass, etc. have been famous and, for a long time, they have been used in many areas such as sealing and encapsulating materials, passivation glass, glaze, etc. Since their physical properties are different between macromolecular materials and low-melting glass, they have been used differently depending upon the environment in which they are used. In general, in case that heat resistance and airtight property have a priority, glass has been used while, in the field where characteristics other than heat resistance and airtight property have a priority, organic materials represented by macromolecular materials have been used. However, as a result of recent progress in the art, characteristics which have not been demanded up to now have received attention and development of materials having such characteristics has been expected.
In view of the above, development for macromolecular materials where heat resistance and airtight property are enhanced and glass where a softening temperature region is made low or the so-called low-melting glass has been briskly carried out. Particularly in the market of electronic materials where heat resistance and airtight property are demanded, low-melting glass represented by a PbO—SiO2—B2O3 type or a PbO—P2O5—SnF2 has been a material which is indispensable in the field of sealing, coating, etc. of electronic parts. In addition, energy required for molding process or, in other words, the cost can be reduced in low-melting glass as compared with high-melting glass and, therefore, that meets the recent social demand for conservation of energy. Further, when it can be melted at the temperature at which an organic material having optical function property is not destructed, its application as a host for (non-linear) optical material containing an optically functioning organic material to optical information communication devices such as optical switch is expected. As such, there has been a demand in many fields for materials having heat resistance and airtight property which are characteristics of common melted glass and also being apt to have various characteristics as in the case of macromolecular materials and, especially, the expectation is concentrated to a low-melting glass. Furthermore, an organic-inorganic hybrid glass has been also receiving public attention as one of the low-melting glass.
With regard to the low-melting glass, Tick glass represented by glass of an Sn—Pb—P—F—O type (refer, for example, to Non-Patent Document 1) is famous for example and, since it has a glass transition point at around 100° C. and also has an excellent water resistance, it has been used in some of the market. However, in this low-melting glass, lead is contained in its main constituting components, there has been a necessity to substitute with other materials due to the recent trend of protection of environment. In addition, demanded characteristic to a low-melting glass represented by Tick glass has been greatly changed and, at the same time, the demand as such has been diversified as well.
With regard to a common method for the production of glass, a fusion method and a low-temperature synthetic method have been known. Fusion method is a method where glass materials are directly heated to melt and make them into glass. Many kinds of glass are produced by this method and a low-melting glass is also produced by this method. In the case of a low-melting glass, however, there are many restrictions for glass composition which can be constituted such as that the containment of lead, alkali, bismuth, etc. is necessary for lowering its melting point.
On the other hand, with regard to a low-temperature synthetic method for noncrystalline bulks, there are sol-gel process, liquid-phase reaction method and anhydrous acid-base reaction method. In a sol-gel process, a metal alkoxide or the like is subjected to a hydrolysis-polycondensation and subjected to a thermal treatment at the temperature of higher than 500° C. (refer, for example, to Non-Patent Document 2), usually at 70 to 1,600° C., whereby a bulk is able to be produced. However, when the bulk produced by a sol-gel process is checked as a material for practical use, there are many cases where the product is porous due to decomposition and burning of organic materials such as alcohol which are introduced in the preparation of the starting solution or evaporation and release, etc. of decomposition gas of organic materials or heating process of water, there is a problem in terms of heat resistance and airtight property. As such, in the production of bulk by a sol-gel process, many problems have been still left unsolved and, particularly, production of low-melting glass by a sol-gel process has not been carried out. Incidentally, it has been also attempted to produce a microlens by pressing a gel film of an organic-inorganic hybrid glass by a sol-gel process coated on a substrate (refer to Non-Patent Document 3).
A liquid-phase reaction method has a low productivity because of its low yield and, in addition, it uses hydrofluoric acid or the like in its reaction system and is limited for the synthesis of a thin film at best. Accordingly, it is almost impossible to use as a practical means for the synthesis of bulks.
An anhydrous acid-base reaction method is a means which has been developed recently and, although it is able to produce an organic-inorganic hybrid glass which is one of the low-melting glasses (refer, for example, to Non-Patent Document 4), it is still in a stage of development and all kinds of low-melting glasses cannot be produced by that.
Accordingly, the production of many kinds of low-melting glasses has been carried out not by a low-temperature synthetic method but by a fusion method. Therefore, due to fusion of glass materials, the glass composition thereof is limited and, with regard to a low-melting glass which can be produced, the type thereof has been very limited.
Incidentally, at present, a low-melting glass is prominent as a material in view of heat resistance and airtight property and it is often that the required physical property is demanded in a form of being represented by the low-melting glass. However, the material is not limited to a low-melting glass but, if the required physical property is satisfied, there is no large problem in low-melting or low-softening material other than glass.
In the publicly known art, there have been disclosed a process for production of quartz glass fibers by a sol-gel process (refer, for example, to Patent Document 1), a process for production of titanium oxide fibers by a sol-gel process (refer, for example, to Patent Document 2) and a process for production of a semiconductor doped matrix by a sol-gel process (refer, for example, to Patent Document 3). There has been also disclosed a low-melting glass of a P2O5—TeO2—ZnF2 type by a fusion method (refer, for example, to Patent Document 4).
[Patent Document 1] JP-A-62-297236
[Patent Document 2] JP-A-62-223323
[Patent Document 3] JP-A-1-183438
[Patent Document 4] JP-A-7-126035
[Non-Patent Document 1] P. A. Tick, Physics and Chemistry of Glasses, Vol. 25, No. 6, pp. 149-154 (1984).
[Non-Patent Document 2] K. Kamiya, S. Sakka and N. Tashiro, Yogyo Kyokaishi, 614-618, 84 (1976).
[Non-Patent Document 3] Atsunori Matsuda, Ceramics, 893-895, 38 (2003)
[Non-Patent Document 4] M. Takahashi, H. Niida and T. Yokoo, New Glass, 8-13, 17 (2002)
The production of many low-softening materials, particularly low-melting glasses, has been carried out by a fusion method. Therefore, there are many restrictions for their glass compositions and, in view of melting materials for the glass, a low-melting glass which can be produced is very limited.
On the other hand, when the production is carried out by a sol-gel process which is a low-temperature synthetic method, a treatment temperature of not lower than 500° C. is necessary for making the product dense but, when the treatment is conducted at such temperature, a low-melting glass is not produced. Therefore, as a result, it has not been possible to produce a low-melting glass having good heat resistance and good airtight property. Particularly in the field of electronic materials, there has been no low-melting glass which copes with severe heat resistance and airtight property and with the production of low-melting ones. In addition, no low-melting material other than glass satisfying heat resistance and airtight property has been found yet.
The methods which are disclosed in JP-A-62-297236, JP-A-62-223323 and JP-A-1-183438 have achievements that the production of materials which were able to produce only by high-temperature fusion is made possible even at low temperature but they are unable to produce a low-melting glass. It is also necessary to treat at not lower than 500° C. after the sol-gel treatment. On the other hand, in a method of JP-A-7-126035, it is disclosed that glass where glass having a transition point of three hundred and several tens degrees centigrade can be produced. However, there has been no example up to now for the production of a glass having a transition point lower than that without a material for making the melting point low such as lead and bismuth.
Thus, according to processes for production of low-melting glass up to now, it was not possible to produce a glass which satisfied both severe heat resistance as well as airtight property and low-melting characteristic. In addition, even in materials other than glass, there has been nothing to satisfy such characteristics.